Justification:Centranthus trinervis is a herbaceous species endemic to Corsica where only a single subpopulation with 140 individuals remains. It is protected at regional, national and international level but a combination of natural and anthropogenic factors could rapidly lead to the extinction of this species in its natural habitat. However, the population and the cliff habitat it survives on are currently stable and the species is therefore assessed as Endangered D.

Centranthus trinervis is endemic to Corsica, and is only known from a single population on the granitic boulders of Trinité near Bonifacio in the southwest of the island. It can be found at sea level. The extent of occurrence is 140 km² and the area of occupancy is less than 10 km².

The single locality holds 140 individuals. Habitat and population are stable. There was an extreme population fluctuation in 1994 when a fire destroyed 80% of the population but it regenerated afterwards (Montmollin and Strahm 2005).

This herbaceous species grows in the shade of rock crevices and along cliff terraces. Only the woody base of this plant persists throughout the entire year, as other above-ground parts dry up at the beginning of summer or are broken by autumn storms. The single subpopulation grows on a cliff.

After a fire, partially burned individuals may regenerate from small suckers at the base. The fruits are dispersed by wind, although regeneration has not been observed outside its present location.

It can be found in Habitats Directive listed habitat 8220 "Siliceous rocky slopes with chasmophytic vegetation" (Commission of the European Communities 2009).

Grazing by goats is a minor threat in lower occurrences of the population and it tends to decrease. In 1994 a fire destroyed 80% of the population but it regenerated afterwards (Montmollin and Strahm 2005). On the other hand, natural fires have been reported to have positive effects on potential competitive species such as Smilax aspera. Although C. ruber has not yet shown signs of being particularly invasive on Corsica, it could hybridize with C. trinervis in the future. A further potential threat could be human disturbance as the population is not far from already developed urban areas. Climbing was reported as a threat in the past as a "via ferrata" was installed at the cliff but this is not the case anymore.

In situ: This species' habitat is included in the Natura 2000 network, it should be managed in a way that favours the conservation of this species. Climbing equipments on the cliff has been removed, population is regularly monitored. The Conservatoire du Littoral bought the area where this species is present as a way to keep the population protected.

Ex situ: Seeds of this species are preserved in several seed banks (e.g. Porquerolles), and cultivated in the botanical gardens of Brest, Porquerolles and in the Jardin Botanique de Lyon (France) and Geneva (Switzerland).

Actions NeededMost urgently, the unique site where this species is found needs to be managed to allow the population to increase. It is essential that the habitat be kept open by clearing competing species such as Smilax aspera, and by eliminating the cultivation of Centranthus ruber and other invasive species grown in the area. Climbing associations as well as the general public need to be made aware about the conservation status of rare plant species in the region.

More field studies and regular monitoring are needed to understand the effect of vegetation cover and density, fires and storms on this species. A replanting programme from seeds collected in situ and plants grown in botanical gardens should be launched.

Commission of the European Communities. 2009. Composite Report on the Conservation Status of Habitat Types and Species as required under Article 17 of the Habitats Directive. Report from the Commission to the Council and the European Parliament. Brussels.